The invention relates to a lock cylinder having a cylinder housing in which a cylinder core is rotatably disposed and which can be locked with the cylinder housing through spring-loaded tumblers by the withdrawal of a key from a key duct of the cylinder core. The lock has a bearing sleeve enclosing the cylinder housing in which the the cylinder housing is rotationally fixed by an overload coupling in the bearing sleeve. A rotary connecting element is arranged behind the lock cylinder and is connected to a locking mechanism by a separating coupling from the cylinder core. The separating coupling is subjected to a forced mechanical control and is operated in response to a relative rotation of the cylinder core with respect to the bearing sleeve.
A lock cylinder of this general type is known from European Pat. No. EP 0 139 550. There, the known lock cylinder and the whole locking mechanism of the lock are combined into a compact structural unit. As long as the lock is unlocked, the cylinder core is form-lockingly connected with a cam disk by means of a separating coupling which is non-rotatably connected with this cylinder core. In contrast, when the lock is locked, the separating coupling is disengaged, with the result that the rotary connection no longer exists between the cylinder core and the cam disk. Since the assigned locking mechanism can be driven only by means of a rotary advancing of the cam disk, it can no longer be actuated by means of the lock cylinder when the separating coupling is disengaged.
Because of this separation of the locking mechanism and the lock cylinder when the lock is locked, the lock cylinder is better protected with respect to violent destruction during break-in attempts.
Specifically, if a "false" key or a tool which is similar to a key shank, such as a screw driver point, is inserted into the keyhole, and an overload torque is exercised on the cylinder core, the cylinder housing, which is locked with the cylinder core by means of the tumblers, rotates in the bearing sleeve as soon as the form-locking, (which exists between the bearing sleeve and the cylinder housing through a ball catch device) is overcome by pressure. In this case, the torque limit of the overload coupling may be dimensioned such that damage to the tumblers as a result of shearing-off stress is avoided. After the cylinder housing is rotated by 360.degree. , the spring-loaded ball of the detent device will again lock in its spherical ball seat at the circumference of the cylinder housing, so that the cylinder housing is again fixed in its initial position.
However, in this known lock cylinder, a permanent rotary connection between the cylinder core and the cam disk acting as the rotary connecting element is not possible without difficulties, because such results in losing the possibility of changing the locking condition of the lock.
Lock cylinders of motor vehicles are known to be arranged separately from the lock as evidenced by German Pat. No. DE-OS 28 22 098. The locked condition of locks of this type is not achieved by a locking at the lock cylinder, but rather in a lever gear of a main plate, which requires a permanent rotary connection between the cylinder core and the lever gear. For this purpose, a rotary connecting element is disposed at the rear end of the lock cylinder, which is non-rotatably connected with the cylinder core, and which, by a revolving rod, is rotationally coupled with the lever gear of the lock. However, this type of a lock cylinder does not provide any protection from damage to the lock cylinder as a result of the aforementioned tampering for the purpose of forcing the lock open.
The invention is based on the object of further developing a lock cylinder of the above-mentioned types so that, while retaining its overload protection, it is also suitable for the rotational control of a locking mechanism arranged separately from the lock cylinder.
This object is achieved by having the separating coupling permanently engaged during rotating movements of the cylinder core with respect to the rotationally fixed cylinder housing, irrespective of the locking condition of the lock, and by having the coupling only be forced into a disengaged position in the course of an overload rotation of the cylinder housing with respect to the bearing sleeve when the disengaging operation is concluded before a certain opening rotational angle of the cylinder core (which is also rotated along), is reached. Thus, the rotary connection between the cylinder core and the rotary connecting element is maintained continuously if the lock cylinder is operated normally with the proper key.
In this case, the control device, particularly in view of the resulting high operational reliability, preferably consists of purely mechanical structural members.
A particularly space-saving construction can be achieved if the separating coupling can be disengaged by an axial movement that extends coaxially with respect to the lock cylinder. Here, a rotation of the cylinder housing in the bearing sleeve can be converted directly into a disengaging movement.
It is advantageous if the rotating movement of the cylinder housing with respect to the bearing sleeve can be converted to the coaxial disengaging advance of the separating coupling. Such an operation is obtained when a ring face of the cylinder housing interacts form-lockingly with a disengaging sleeve, which is non-rotatably held in the bearing sleeve and is subjected to an axial spring load.
The form locking mechanism comprises two detent cams which engage in assigned detent indentations. The separating coupling has a forked claw which is a component of a sliding claw and is guided axially on a driver shaft of the rotary connecting element. The forked claw projects out of the cylinder core side, while being non-rotatably supported at the cylinder core in the engaged condition. The sliding claw has two diametrically arranged forked claws which form-lockingly reach around two drivers fixed at the cylinder core.
The disengaging sleeve is slidingly disposed in the bearing sleeve, by axial sliding devices. An outer circumference of the sliding claw is axially moveable and supported in a rotatably disposed manner and is surrounded by an inwardly bent guiding neck of the disengaging sleeve.
The guiding neck is molded to the disengaging sleeve and is recessed with respect to the outer circumference. One end of a compression spring is supported on the face of the disengaging sleeve between the guiding neck and the inner circumference of the bearing sleeve. A rear end of the bearing sleeve can be closed off by a bearing cover and the compression spring is prestressable by a bearing cover flange of the cover which telescopically engages in the bearing sleeve.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.